this import wizard is mainly for importing non 4diac projects from other tools (e..g, FBDK) into 4diac. As with your correct checkout of the examples from our mercurial repo you already have 4diac projects. You can use the "Import -> General -> existing projects into workspace" wizard which should be more convenient in your case.

But to also answer your question regarding the folder in this specific case of a 4diac project the folder would be the same as where your .sys file is located.